Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis is intended to refer to the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal is intended to refer to the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels corresponding terms such as caudal and cranial should be understood.
In recent years, endovascular implantable devices have been developed for treatment of aortic aneurysms, wherein the devices are delivered to the treatment site through the vascular system of the patient rather than by open surgery. Such devices generally include a tubular or cylindrical frame work or scaffolding of one or more stents to which is secured a tubular shape of graft material such as woven DACRON polyester (trade mark of E I Dupont de Nemours and Co.), polytetrafluoroethylene (PTFE) and the like. These devices are initially reduced to a small diameter and placed into the leading or proximal end of a catheter delivery system. The delivery system is inserted into the vascular system of the patient such as through a femoral incision. The leading end of the delivery system is maneuvered to the treatment site over a previously positioned guide wire. Through manipulation of control systems that extends to the proximal end of the catheter from the distal end of the system outside the patient, the device is then deployed by holding the device at its location and withdrawing the surrounding sheath, whereafter the stent graft self expands or is expanded through use of a balloon therewith that is expanded. The stent graft becomes anchored in position to healthy vessel wall tissue in the aorta such as by barbs, whereafter the delivery system is then removed leaving the device in position traversing the aneurysm in a manner that channels all blood flow through the stent graft so that no blood flow enters the aneurysm thereafter, such that not only does the aneurysm no longer continue to grow and possibly rupture but the aneurysm actually beings to shrink and commonly disappears entirely.
For treatment of abdominal aortic aneurysms in particular, bifurcated stent grafts are known wherein a pair of leg sections extend from the end of the stent graft and are disposed in the iliac arteries in the bifurcation of the aorta and iliac arteries, while the opposite end of the stent graft is anchored to the aorta wall adjacent to the renal arteries, usually by means of an attachment stent having barbs that penetrate harmlessly into the vessel wall so that blood flow does not displace the stent graft from its precise location. One such bifurcation stent graft is the ZENITH AAA stent graft sold by William A. Cook Australia Pty Ltd., Brisbane, Queensland, Australia.
Another example of such a stent graft is disclosed in PCT Publication No. WO 98/53761 in which the stent graft includes a sleeve or tube of biocompatible graft material defining a lumen, and further includes several stents secured therealong, with the stent graft spanning the aneurysm extending along the aorta proximally (ie towards the heart) from the two iliac arteries. The reference also discloses the manner of deploying the stent graft in the patient utilizing an introducer assembly. The graft material-covered portion of the single-lumen proximal end of the stent graft bears against the wall of the aorta above the aneurysm to seal the aneurysm at a location that is spaced distally (ie away from the heart) of the entrances to the renal arteries. Thin wire struts of a proximal stent extension traverse the renal artery entrances without occluding them, since no graft material is utilized along that portion of the proximal stent, while securing the stent graft in position within the aorta when the stent graft self-expands. An extension is affixed to one of the legs of the stent graft to extend along a respective iliac artery and, optionally, extensions may be affixed to both legs.
However, for an aneurysm that develops in the thoracic arch of the aorta, stent grafts are needed that are deployable to extend along the substantial curvature of the arch without occluding the main branch vessels joined to the aorta along the arch's curve, all of which may be involved in and compromised by the aneurysm.